The present invention relates to roller chains and sprockets and specifically relates to a buffer mechanism at the coupling thereof.
Roller chains and sprockets have long been used as a means for transmitting power, timing rotary components and the like. One difficulty associated with such chain and sprocket arrangements is the impact of the chain rollers on the sprocket as they engage. This impact creates excessive noise and excessive wear. This impacting and the noise associated therewith are illustrated in FIG. 1 as resulting from the roller 10 of a chain, schematically illustrated as 12, impacting against the tooth 14 of a sprocket 16 as the chain length 12 bends and oscillates to engage the sprocket 16. The loudest noise is said to occur at the engagement starting point 18 which occurs as indicated by the distribution curve 20 along the travel of the chain.
Because of the noise and wear associated with conventional roller chain and sprocket couplings, devices have been developed in an effort to reduce these problems. These devices have attempted to buffer the chain at this range of points 18. A first such device is illustrated in FIGS. 2 and 3 and includes circular peripheral grooves 22 and 24 on a sprocket 26 on either side of the sprocket teeth 28. Located within the grooves 22 and 24 are resiliently compressible buffer rings 30 and 32. These buffer rings 30 and 32 fit snugly in the grooves 22 and 24 because of their exceptionally resilient nature.
The buffer rings of FIGS. 2 and 3 provide the buffering effect through the resilient restoring force against compression of the rings 30 and 32 in resisting the link plates 34 of the chain 36. This mechanism successfully reduces noise. However, because of the fixed location of the buffer rings 30 and 32 relative to the sprocket 26 and sprocket teeth 28, rapid wear and fatigue is experienced at fixed points on the rings 30 and 32 such that the device becomes relatively impractical.
A second type of buffer ring heretofore known is illustrated in FIGS. 4 and 5. The sprocket 26 again includes circular peripheral grooves 22 and 24 on either side of the sprocket teeth 28 to accommodate metallic buffer rings 38 and 40. The metallic buffer rings 38 and 40 have an inner diameter which is larger than the outer diameter of the bottom of either of the grooves 22 and 24. Also, the buffer rings 38 and 40 have a radial thickness which is less than or equal to the depth of the bottom of the grooves 22 and 24 below the inscribed circle of the link plates of the roller chain where it engages the sprocket. This inscribed circle is identified in FIG. 4 by the numeral 42. The outside diameter of the metallic buffer rings 38 and 40 are also greater than the inscribed circle of the link plates 42.
This latter type of buffer ring, as illustrated in FIGS. 4 and 5, operate solely on deflection, which acts to deform the ring from its circular shape, as illustrated in FIG. 4. The ring material itself is not compressed between the link plates of the chain 36 and the bottom of the grooves 22 and 24 as in the device of FIGS. 2 and 3. An advantage of the metallic buffer rings is that they constantly change position with respect to the teeth 28 of the sprocket 26 and, hence, do not have fixed wear spots. Because of this distortion, the point of application of the effective resilient restoring force provided by the metallic buffer rings 38 and 40 moves to the right, as seen in FIG. 4, away from the point of greatest impact. Consequently, maximum noise abatement cannot be achieved.